1. Technical Field
The present disclosure relates generally to a surgical access apparatus employing a system for maintaining a fluid-tight seal across a passageway for surgical instruments. In particular, the disclosure relates to a portal apparatus employing a variable diameter winepress seal in communication with a power source for accommodating instruments of various sizes.
2. Background of Related Art
Surgical procedures such as laparoscopic, arthroscopic, and endoscopic procedures in general are termed minimally invasive at least in part because the incision required is relatively small, perhaps one inch in length or less. Small incisions are preferred because they are inherently less traumatic to the surrounding body tissue. Also, small incisions subject internal organs to a limited exposure to the contaminants in the outside atmosphere. Thus, small incisions enable shorter hospital stays and faster recoveries with less pain and scarring than is common with the larger incisions required for conventional surgery.
Endoscopic surgery is possible due in part to the availability of instruments designed specifically for this purpose. A trocar assembly, for example, may include a sharp trocar or obturator for creating a small incision, and a cannula assembly for providing a conduit through the incision once the obturator has been removed. A cannula is an elongated tube, e.g., 2 mm to 15 mm in diameter, which may be configured to have a distal or leading end inserted into an internal body cavity adjacent an operative site. The body cavity is often inflated with an insufflation gas, carbon dioxide, for example, to separate the body wall from vital organs. This provides a space where a surgeon may introduce viewing equipment or maneuver tools into position without damaging surrounding tissue. Various other instruments may then be inserted and withdrawn through the cannula for access to the working space and operative site. In order to fit through a cannula and enable a surgeon to manipulate tissue far removed from the incision, instruments adapted for endoscopic surgery typically include a long and narrow cylindrical shaft. The exact size and shape of the instrument shaft may vary for the several instruments commonly required for a single procedure.
Endoscopic procedures generally require that any instrumentation inserted into the patient's body be sealed, e.g., provisions must be made to ensure insufflation gas does not escape the body through the cannula. Furthermore, a seal acts to prevent contamination of the body cavity by the outside environment. In the absence of such a fluid-tight seal, many of the attendant advantages of minimally invasive surgery are lost. In order to maintain a seal at all times, e.g., before, during and after the introduction of an instrument into the cannula, a dual seal system is commonly employed. A first seal is normally biased to a closed condition to seal the conduit in the absence of an instrument. Because the first seal may be defeated upon the introduction of an instrument, a second seal may be positioned to establish a sealing relation with the shaft of the instrument before the first seal is compromised.
The second seal is often configured with a variable diameter orifice to be adaptable to various sizes and geometries associated with the instrument shafts. A septum seal, for example is a generally flat, elastomeric member having an expandable orifice therethrough. The orifice may be sized such that the smallest instrument may not pass through the septum seal without engaging and forming a seal with the elastic material. The elasticity of the septum seal permits the orifice to expand to accommodate the largest instrument.
An aspect of concern in the use of such a septum seal is the contact pressure applied by the septum seal on the instrument shaft. If the contact pressure is insufficient, the insufflation pressure may not be maintained as the surgeon manipulates the instrument. If the contact pressure is too great, however, the surgeon may experience difficulty in advancing and properly controlling the instrument. Because lager instruments must expand the orifice to a greater degree, the contact pressure is consequently larger than for smaller instruments, and thus larger instruments may be more difficult to manipulate than smaller instruments. Accordingly, a need exists for an apparatus for forming a seal about an instrument inserted through a cannula that is capable of accommodating variously sized instruments while ensuring an appropriate contact pressure.